1. Field of the Invention
The present invention relates to a transfer-type photo-sensitive sheet suitable for a printing paper for a light printing device such as a light printer and a copier.
2. Prior Art
A transfer-type photo-sensitive sheet comprises a photo-sensitive sheet coated with microcapsules containing chromogen, photo-sensitive resin, photo sensitizer, polymerization initiator and others, and a transfer sheet coated with developing agent which causes development reaction on the chromogen. U.S. Pat. No. 4,399,209 discloses such photo-sensitive sheet.
For example, if this transfer-type photo-sensitive sheet is used for a copier, as shown in a schematic illustration of FIG. 5, light emitted from a light source 1 scans a surface of an original 2 and the reflected light is struck on the surface of a photo-sensitive sheet 4 via a lens 3 to form a light latent image thereon. Subsequently, a transfer sheet 5 fed by a transfer sheet feed roller 7 of another system is superimposed on the photo-sensitive sheet 4 to be fed between pressure developing rollers 6. Thus, non-hardening microcapsules on the photo-sensitive sheet 4 are broken by pressure and development reaction is caused by chromogen therein and developing agent on the transfer sheet 5, thereby allowing an image to appear on the transfer sheet
In this case, in order to develop the image up to the circumferential end of the transfer sheet 5, as shown in FIG. 6, when a photo-sensitive sheet 4 and a transfer sheet 5 are used in a form of cut sheet, the circumferential ends of the photosensitive sheet 4 project from the transfer sheet 5. As shown in FIG. 7, when the sheets 4 and 5 form a roll sheet respectively, the photo-sensitive sheet 4 is wider than the transfer sheet 5.
However, prior to the present invention, the whole surface of the photo-sensitive sheet 4 is coated with the microcapsules 8 as shown in FIGS. 6 and 7, whether it is a cut paper or a roll one. Accordingly, as shown in FIG. 8, when the photo-sensitive sheet 4 with the transfer sheet 5 superimposed thereon is fed through the transfer rollers 6, the non-hardening microcapsules 8 on the photosensitive sheet 4 are then broken by the pressure of the transfer rollers. Since the circumferential ends of the photo-sensitive sheet 4 project from the transfer sheet 5, the chromogenic materials and the photo-sensitive resin encapsulated in the microcapsules adhere to the surface of the transfer rollers on which only the photo-sensitive sheet 4 passes. The gradual accumulation of the attachment due to the continuative use of a light printing device causes fluctuation of a preset pressure of the pressure developing rollers 6, resulting in that the non-hardening microcapsules 8 are not entirely broken by pressure of the rollers 6. In other words, uneven development of the transfer sheet 5 is caused thereby. Further, there is some trouble for maintenance in that the frequent cleaning of the pressure developing rollers 6 is required since the attachment thereof makes the sequential transfer sheet dirty.